This specification relates to generating summaries of resources.
The Internet provides access to a wide variety of resources, such as video and/or audio files, and web pages for particular subjects. A search system provides search results in response to users' search queries. Often, to help users to select a search result, the results page displays a summary, or a snippet, for each of the search results. To determine what text content to be included in the summary, the search engine automatically crawls the web and tries to identify useful text content in a webpage. However, it sometimes may be difficult to automatically identify and extract the useful text content in some webpages because the section that includes the useful text content is often mixed with sections that provide other text content that does not directly related to the subject matter of the webpage, such as advertisements, weather, etc.